The Applicant are familiar with the concept of aliasing in signal processing (http://en.wikipedia.org/wiki/Aliasing, accessed 18 Feb. 2015). Aliasing in the form of temporal aliasing is practically observable when a video camera operating at a particular sampling rate captures a cyclically moving object and the video of the subject shows the object moving at a false speed. This is colloquially known as the wagon-wheel effect (http://en.wikipedia.org/wiki/Wagon-wheel_effect, access 18 February 2015) and more scientifically as the stroboscopic effect (http://en.wikipedia.org/wiki/Stroboscopic_effect, accessed 18 Feb. 2015).
It is specifically this temporal aliasing effect which the Inventors wish to utilise to control display of a cyclically moving object in a video. However, this is difficult because there are two main factors which influence temporal aliasing, namely i) sampling rate of the camera and ii) frequency of the cyclically moving object, are not practically controllable.
Video cameras typically sample at industry-defined sampling rates or frequencies. Video footage intended for television display is usually provided at 24 or 30 FPS (Frames Per Second) or newer HFR (High Frame Rate) at 60 FPS. Some video cameras have adjustable sampling rates, while others have fixed sampling rates. Even if a video camera has an adjustable sampling rate, it might not be possible to adjust it in real-time, or if it is, it may be undesirable to have video captured at continuously varying sampling rates.
Controlling the frequency of the cyclically moving object is even more impracticable. The object may be a wheel of a car or bike, or a rotor of a plane or helicopter (for example). These objects usually cycle or rotate at frequencies dictated by an operation (e.g., speed) of the vehicle to which they are mounted. Fixing the operation of the vehicle to match the frequency of the cyclically moving object to the sampling rate of the camera is highly impractical.
Accordingly, the Inventors desire a system and method which permits control of the temporal aliasing of video captured of a cyclically moving object without needing to adjust the sampling rate of the video camera or the frequency of the cyclically moving object.
The closest disclosures of which the Applicant is aware are as follows:                CA2455114 discloses placement of a rotary mask over a rotating objected, the speed of the rotating mask being controllable (in one embodiment) by an external controller.        U.S. Pat. No. 2,745,092 discloses a method of illuminating indicia on a wheel. A strobe light is matched to a period of rotation of the wheel to display a particular number.        U.S. Pat. No. 9,119,266 discloses a handheld strobe light but the frequency of the strobe is not matched to an externally cyclical object.        WO2009133403 discloses downsampling a high framerate could intentionally introduce temporal aliasing effects such as the wagon wheel effect.        CN1554926 discloses projecting a grid pattern onto a cyclically moving object in order to measure deformation characteristics of the cyclically moving object by rendering a three-dimensional model of the object.        